Just got a brand new Kia Soul with bluetooth audio and phone. My setup from the car side has an option to pull the contacts. It took about 20 seconds to transfer all my contacts over and everything worked perfectly. Music continued to stream and I even made a few test calls. Everything worked perfectly. My guess is that every car manufacturer implements their own solution and it either works well with any given phone or it doesn't. It looks like a crap shoot to me. I'd say that if it works on some cars and not on others, then the problem is likely to be with the car's solution and not on the phone.